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I'm still trying to determine what rear end I have in my Nova. I've taken it down and found it has a 30 spline pinion and the square notches on the carrier as indicated in Nova Resources site for an 8.5 carrier. I'll try to insert a few pics I've taken. Also, the ring gear maesures 8.5 inches. I guess this is an 8.5 rear but, the ring and pinion indicates 71 as the year. I'm just not sure?

The passengers side axle tube has these letters and numbers: JD G340 2.

Tha axles are 28 spline, the pinion is 30 spline. The Nova Resource differential page shows a carrier housing with 2 pronounced square lugs or blocks on the bottom indicating it's an 8.5 rear, my carrier has these lugs. The open carrier has a GM6 and 495N opposite the ring gear mounting flange. There is also an L 2 1 on the carrier housing which if I'm right, mean the housing was manufactured December 2nd 1971. The numbers on the ring gear are: 2 GM 3984828 13 40 71 2 the pinion numbers are: 71 3984829 13 40 GM
Thanks for the help guy's
Mac

The 13 and 40 indicates a 3.08 ring and pinion ratio. I think those 71 numbers on the gears are date codes. The "340" is the housing date code which is December 6. You may have one of the last 1971's made and GM used a new for 1972 "JB" 2.73 ratio 8.5" ten bolt rear axle with 3.08 gears. Who knows? Stranger things have happened at GM.

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